1. Field of the Invention
The present invention relates to a subcutaneous fat thickness measuring method of optically measuring the thickness of local subcutaneous fat, a subcutaneous fat thickness measuring apparatus, a program and a recording medium.
2. Related Art of the Invention
As shown in FIG. 13, there is a conventional method of measuring the thickness of subcutaneous fat 4 in a living body by a light receiving element 3 receiving light that is launched into the living body by a light source 2 on a surface of a living body 1, passes through the living body while being scattered and absorbed therein, and then emerges from the surface of a living body (for example, see Japanese Patent Laid-Open No. 2000-155091). The entire disclosure of the above document is incorporated herein by reference in its entirety. In addition, in the above document, there is disclosed a method of compensating for a variation due to a difference of the color of a skin 5 using the quantity of light received by a light receiving element 3 disposed near the light source.
The muscle and the fat have significantly different light propagation characteristics. The muscle absorbs more light, and the fat scatters more light. The difference in light propagation characteristics is remarkable for light having a wavelength between 500 nm and 1000 nm. Therefore, as the subcutaneous fat 4 becomes thicker, more light launched by the light source 2 into the surface of a living body is scattered in the subcutaneous fat 4 and is diffused not only in the depth direction but also in the lateral direction.
Thus, the light diffused in the lateral direction and emerges from the surface of a living body 1 increases according to increment of the thickness of the subcutaneous fat 4. The thickness and the amount of the subcutaneous fat 4 can be determined by the light receiving element 3 receiving the light emerging from the surface of a living body 1.
In addition, according to this method, the light source 2 and plural light receiving elements 3 are disposed so that plural light-reception-to-light-emission lengths can be obtained. That is, in determining the quantity of light received by each light receiving element 3, an error due to a difference of the color of the skin 5 is compensated for using the quantity of light received by the light receiving element disposed closest to the light source 2.
However, although the conventional subcutaneous fat thickness measuring apparatus described above can correct an error due to a difference of the color of the skin 5, it cannot correct an error due to a variation of light absorption by the subcutaneous fat 4, which is caused by a variation of the blood amount.
The subcutaneous fat 4 of a human body, which is a measuring object, has a network of blood vessels and can effectively be regarded as a uniform organization. However, the amount of the blood flowing through the organization varies due to exercise or sleep, which causes the blood concentration to vary, which causes the light absorption by the subcutaneous fat 4 to vary.
As described above, the conventional subcutaneous fat thickness measuring apparatus has a problem that it cannot correct an error due to a variation of light absorption by the subcutaneous fat 4.